Fix potential bug in Xlib event polling.
Fix potential bug in Xlib event polling.

theblacklion/pyglet,adamlwgriffiths/Pyglet,theblacklion/pyglet,mammadori/pyglet,niklaskorz/pyglet,theblacklion/pyglet,mammadori/pyglet,niklaskorz/pyglet,mammadori/pyglet,niklaskorz/pyglet,adamlwgriffiths/Pyglet,oktayacikalin/pyglet,oktayacikalin/pyglet,seeminglee/pyglet64,seeminglee/pyglet64,adamlwgriffiths/Pyglet,oktayacikalin/pyglet,theblacklion/pyglet,theblacklion/pyglet,adamlwgriffiths/Pyglet,niklaskorz/pyglet,oktayacikalin/pyglet,seeminglee/pyglet64,oktayacikalin/pyglet,mammadori/pyglet